More than a thousand white storks call Switzerland their summer home. A study has also found that fewer are migrating to Africa in the winter.
Last summer bird specialists counted 470 adults (in couples) and 757 young ones. The species had almost disappeared from the country 70 years ago and storks from Algeria had to be introduced. The rise in numbers could be explained by a decrease in mortality due to a change in migratory patterns.
Based on bird ringing data, it is very rare for a stork spending the summer in Switzerland to migrate as far as the African Sahel, their traditional wintering grounds. Those that do leave fly no further than southern Spain or Portugal. In total, around 360 gave up on migrating altogether. A research project is underway to determine why the birds choose to stay put.
Peter Enggist, director of the Swiss Stork Societyexternal link that was responsible for the census, has his own hypothesis. According to him, the migration distance is genetically programmed in the birds. As storks introduced into post-war Switzerland are of Algerian origin, they migrate a shorter distance: the migration path of Algerian storks to Central Africa is equivalent to that between Switzerland and Spain or Portugal.
Other Swiss experts say experience plays an important role. The oldest storks migrate the least as their experience makes it easier for them to find food in winter conditions compared to an inexperienced young bird, said Livio Rey of the Sempach Ornithological Station.